Plasma fibronectin deficiency often exists in septic surgical, trauma and burn patients with altered lung vascular permeability. This plasma fibronectin (Fn) deficiency may contribute to the etiology of decreased endothelial integrity and pulmonary edema. Plasma Fn incorporates into the extracellular matrix (ECM) of the lung where it influences cell-matrix interactions and endothelial protein permeability, in part, by its interaction with endothelial cell surface integrins. The investigators have demonstrated that infusion of purified human plasma Fn into sheep followed by its incorporation into the lung ECM prior to post- operative gram negative i.v. bacterial challenge will prevent the increase in lung protein permeability. The is vivo observation could also be "modeled" in vitro using confluent lung endothelial cell monolayers treated with TNF, which results in an increase in protein permeability and a disruption of the Fn containing matrix. Addition of purified human Fn to the medium could also prevent the TNF-alpha induced increase in endothelial monolayer permeability similar to the in vivo response, if the added plasma Fn incorporates into the subendothelial matrix. The investigators hypothesize that the TNF- alpha induced increase in lung permeability is mediated by either decreased expression of a5b1 Fn integrins on endothelial cells an/or disruption of the Fn matrix due to protease release from endothelial cells. It is also hypothesized that the protective and potentially therapeutic effects of Fn on lung endothelial permeability is due to its rapid incorporation into the ECM where it provides additional RGD cell attachment sites, improves endothelial adhesion, and influences endothelial cell spreading via an integrin-mediated signal transduction process. It is proposed to use the lung lymph fistula model in sheep to determine if the increase in lung endothelial permeability caused by post-operative bacteremia can be reversed by infusion of purified PFN; and the in vitro bovine lung endothelial cell monolayer model to define the mechanism of the TNF-alpha induced increase in protein permeability. The investigators will also determine if reversal of the increased permeability accomplished by the ECM incorporation of human plasma Fn requires an integrin mediated signal transduction event triggered by a reestablished association of a5b1 integrins with human Fn incorporated into the matrix. Determining the mechanism by which plasma Fn incorporation into the lung matrix influences its vascular integrity offers a basis for developing a novel approach to treat lung vascular failure and pulmonary edema in septic surgical and trauma patients.